OpenCV  3.2.0-dev
Open Source Computer Vision
cv::SimpleBlobDetector Class Reference

Class for extracting blobs from an image. More...

#include "features2d.hpp"

Inheritance diagram for cv::SimpleBlobDetector:
Collaboration diagram for cv::SimpleBlobDetector:

Classes

struct  Params
 

Public Member Functions

virtual void clear ()
 Clears the algorithm state. More...
 
virtual void compute (InputArray image, std::vector< KeyPoint > &keypoints, OutputArray descriptors)
 Computes the descriptors for a set of keypoints detected in an image (first variant) or image set (second variant). More...
 
virtual void compute (InputArrayOfArrays images, std::vector< std::vector< KeyPoint > > &keypoints, OutputArrayOfArrays descriptors)
 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. More...
 
virtual int defaultNorm () const
 
virtual int descriptorSize () const
 
virtual int descriptorType () const
 
virtual void detect (InputArray image, std::vector< KeyPoint > &keypoints, InputArray mask=noArray())
 Detects keypoints in an image (first variant) or image set (second variant). More...
 
virtual void detect (InputArrayOfArrays images, std::vector< std::vector< KeyPoint > > &keypoints, InputArrayOfArrays masks=noArray())
 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. More...
 
virtual void detectAndCompute (InputArray image, InputArray mask, std::vector< KeyPoint > &keypoints, OutputArray descriptors, bool useProvidedKeypoints=false)
 Detects keypoints and computes the descriptors. More...
 
virtual bool empty () const
 Return true if detector object is empty. More...
 
virtual String getDefaultName () const
 Returns the algorithm string identifier. More...
 
void read (const String &fileName)
 
virtual void read (const FileNode &)
 Reads algorithm parameters from a file storage. More...
 
virtual void save (const String &filename) const
 Saves the algorithm to a file. More...
 
void write (const String &fileName) const
 
virtual void write (FileStorage &) const
 Stores algorithm parameters in a file storage. More...
 

Static Public Member Functions

static Ptr< SimpleBlobDetectorcreate (const SimpleBlobDetector::Params &parameters=SimpleBlobDetector::Params())
 
template<typename _Tp >
static Ptr< _Tp > load (const String &filename, const String &objname=String())
 Loads algorithm from the file. More...
 
template<typename _Tp >
static Ptr< _Tp > loadFromString (const String &strModel, const String &objname=String())
 Loads algorithm from a String. More...
 

Protected Member Functions

void writeFormat (FileStorage &fs) const
 

Detailed Description

Class for extracting blobs from an image.

:

The class implements a simple algorithm for extracting blobs from an image:

  1. Convert the source image to binary images by applying thresholding with several thresholds from minThreshold (inclusive) to maxThreshold (exclusive) with distance thresholdStep between neighboring thresholds.
  2. Extract connected components from every binary image by findContours and calculate their centers.
  3. Group centers from several binary images by their coordinates. Close centers form one group that corresponds to one blob, which is controlled by the minDistBetweenBlobs parameter.
  4. From the groups, estimate final centers of blobs and their radiuses and return as locations and sizes of keypoints.

This class performs several filtrations of returned blobs. You should set filterBy* to true/false to turn on/off corresponding filtration. Available filtrations:

  • By color. This filter compares the intensity of a binary image at the center of a blob to blobColor. If they differ, the blob is filtered out. Use blobColor = 0 to extract dark blobs and blobColor = 255 to extract light blobs.
  • By area. Extracted blobs have an area between minArea (inclusive) and maxArea (exclusive).
  • By circularity. Extracted blobs have circularity ( \(\frac{4*\pi*Area}{perimeter * perimeter}\)) between minCircularity (inclusive) and maxCircularity (exclusive).
  • By ratio of the minimum inertia to maximum inertia. Extracted blobs have this ratio between minInertiaRatio (inclusive) and maxInertiaRatio (exclusive).
  • By convexity. Extracted blobs have convexity (area / area of blob convex hull) between minConvexity (inclusive) and maxConvexity (exclusive).

Default values of parameters are tuned to extract dark circular blobs.

Member Function Documentation

virtual void cv::Algorithm::clear ( )
inlinevirtualinherited

Clears the algorithm state.

Reimplemented in cv::FlannBasedMatcher, cv::DescriptorMatcher, and cv::cuda::DescriptorMatcher.

virtual void cv::Feature2D::compute ( InputArray  image,
std::vector< KeyPoint > &  keypoints,
OutputArray  descriptors 
)
virtualinherited

Computes the descriptors for a set of keypoints detected in an image (first variant) or image set (second variant).

Parameters
imageImage.
keypointsInput collection of keypoints. Keypoints for which a descriptor cannot be computed are removed. Sometimes new keypoints can be added, for example: SIFT duplicates keypoint with several dominant orientations (for each orientation).
descriptorsComputed descriptors. In the second variant of the method descriptors[i] are descriptors computed for a keypoints[i]. Row j is the keypoints (or keypoints[i]) is the descriptor for keypoint j-th keypoint.
virtual void cv::Feature2D::compute ( InputArrayOfArrays  images,
std::vector< std::vector< KeyPoint > > &  keypoints,
OutputArrayOfArrays  descriptors 
)
virtualinherited

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Parameters
imagesImage set.
keypointsInput collection of keypoints. Keypoints for which a descriptor cannot be computed are removed. Sometimes new keypoints can be added, for example: SIFT duplicates keypoint with several dominant orientations (for each orientation).
descriptorsComputed descriptors. In the second variant of the method descriptors[i] are descriptors computed for a keypoints[i]. Row j is the keypoints (or keypoints[i]) is the descriptor for keypoint j-th keypoint.
static Ptr<SimpleBlobDetector> cv::SimpleBlobDetector::create ( const SimpleBlobDetector::Params parameters = SimpleBlobDetector::Params())
static
virtual int cv::Feature2D::defaultNorm ( ) const
virtualinherited
virtual int cv::Feature2D::descriptorSize ( ) const
virtualinherited
virtual int cv::Feature2D::descriptorType ( ) const
virtualinherited
virtual void cv::Feature2D::detect ( InputArray  image,
std::vector< KeyPoint > &  keypoints,
InputArray  mask = noArray() 
)
virtualinherited

Detects keypoints in an image (first variant) or image set (second variant).

Parameters
imageImage.
keypointsThe detected keypoints. In the second variant of the method keypoints[i] is a set of keypoints detected in images[i] .
maskMask specifying where to look for keypoints (optional). It must be a 8-bit integer matrix with non-zero values in the region of interest.

Reimplemented in cv::AgastFeatureDetector_Impl.

virtual void cv::Feature2D::detect ( InputArrayOfArrays  images,
std::vector< std::vector< KeyPoint > > &  keypoints,
InputArrayOfArrays  masks = noArray() 
)
virtualinherited

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Parameters
imagesImage set.
keypointsThe detected keypoints. In the second variant of the method keypoints[i] is a set of keypoints detected in images[i] .
masksMasks for each input image specifying where to look for keypoints (optional). masks[i] is a mask for images[i].
virtual void cv::Feature2D::detectAndCompute ( InputArray  image,
InputArray  mask,
std::vector< KeyPoint > &  keypoints,
OutputArray  descriptors,
bool  useProvidedKeypoints = false 
)
virtualinherited

Detects keypoints and computes the descriptors.

virtual bool cv::Feature2D::empty ( ) const
virtualinherited

Return true if detector object is empty.

Reimplemented from cv::Algorithm.

virtual String cv::Algorithm::getDefaultName ( ) const
virtualinherited

Returns the algorithm string identifier.

This string is used as top level xml/yml node tag when the object is saved to a file or string.

template<typename _Tp >
static Ptr<_Tp> cv::Algorithm::load ( const String filename,
const String objname = String() 
)
inlinestaticinherited

Loads algorithm from the file.

Parameters
filenameName of the file to read.
objnameThe optional name of the node to read (if empty, the first top-level node will be used)

This is static template method of Algorithm. It's usage is following (in the case of SVM):

Ptr<SVM> svm = Algorithm::load<SVM>("my_svm_model.xml");

In order to make this method work, the derived class must overwrite Algorithm::read(const FileNode& fn).

References cv::Ptr< T >::empty(), cv::FileNode::empty(), cv::FileStorage::getFirstTopLevelNode(), and cv::FileStorage::READ.

Here is the call graph for this function:

template<typename _Tp >
static Ptr<_Tp> cv::Algorithm::loadFromString ( const String strModel,
const String objname = String() 
)
inlinestaticinherited

Loads algorithm from a String.

Parameters
strModelThe string variable containing the model you want to load.
objnameThe optional name of the node to read (if empty, the first top-level node will be used)

This is static template method of Algorithm. It's usage is following (in the case of SVM):

Ptr<SVM> svm = Algorithm::loadFromString<SVM>(myStringModel);

References CV_WRAP, cv::Ptr< T >::empty(), cv::FileNode::empty(), cv::FileStorage::getFirstTopLevelNode(), cv::FileStorage::MEMORY, and cv::FileStorage::READ.

Here is the call graph for this function:

void cv::Feature2D::read ( const String fileName)
inherited
virtual void cv::Feature2D::read ( const FileNode fn)
virtualinherited

Reads algorithm parameters from a file storage.

Reimplemented from cv::Algorithm.

virtual void cv::Algorithm::save ( const String filename) const
virtualinherited

Saves the algorithm to a file.

In order to make this method work, the derived class must implement Algorithm::write(FileStorage& fs).

void cv::Feature2D::write ( const String fileName) const
inherited
virtual void cv::Feature2D::write ( FileStorage fs) const
virtualinherited

Stores algorithm parameters in a file storage.

Reimplemented from cv::Algorithm.

void cv::Algorithm::writeFormat ( FileStorage fs) const
protectedinherited

The documentation for this class was generated from the following file: